The present invention relates to a urine testing apparatus, and particularly to a urine testing apparatus capable of obtaining accurate urine specific gravity and urine glucose level (urinary glucose value).
In the point of test and therapy of diabetes, it is important to know urine glucose level (urinary glucose value). The urinary glucose value is, as a rule, evaluated by measuring glucose amount contained in total urine excreted for 24 hours (total excreted urine). Practically, the urinary glucose value is measured after urine is accumulated for one day (accumulation of urine) in a container. However, operation of these steps is complicated allowing to apply to hospitalized patients only. In contrast to the total excreted urine, once excreted urine is named partial urine (urine excreted in each individual occasion). At present, in outpatients, group examination, and home therapy, the measurement of the urinary glucose value of the total excreted urine has been replaced by that of the partial urine, using urine test paper or a urinary glucose meter. However, the urinary glucose value changes according to urine amount to result in occasional inconsistency between urinary glucose values of the partial urine and total excreted urine. This defect causes inaccurate diagnosis.
Therefore, a method has been proposed to measure and correct the urinary glucose value of the partial urine. For example, in a journal (Igaku Kensa 43: 1839-1845. 1994), it has been reported that measurement is carried out for urine specific gravity of the partial urine and urinary glucose value of the partial urine is corrected with the urine specific gravity on the basis of the following formula (1) to estimate the urinary glucose value of total excreted urine. ##EQU1## wherein 1.015 means the standard value of the urine specific gravity in urine accumulation for 24 hours.
In Unexamined Japanese Patent Publication No.9262/1991, a urine testing apparatus is disclosed to indicate the critical degree of diabetes through the fuzzy processing of the result of the measurement of urinary glucose value, urine pH, and urine specific gravity of the partial urine. In the urine testing apparatus disclosed therein, measuring methods of the urinary glucose value and the urine pH are an optical reading method for the coloring degree of test paper of coloring reaction and a method of electric detection using an enzyme electrode. However, any measuring method of the urine specific gravity has never been described. Besides, a relationship between the urinary glucose value and the urine specific gravity has not described, but a fuzzy processing has been only presented in the publication.
In the interim, weight method, areometry, falling method, and refractometry is commonly known for measurement of urine specific gravity. Though these methods are accurate, requires expensive measuring instruments and are time-consuming for operation. Thus, an indirect method based on chemical properties has been invented. This method named test paper method for specific gravity is done by measuring a cation concentration in urine to read specific gravity from the correlation of the cation concentration and specific gravity. For example, macromolecular electrolyte (methoxyethylene--maleic acid anhydride copolymer), buffer solution, and pH indicator (bromothymol blue: yellow color changes to blue at pH 6.2-7.8) are applied to a base material. Cations contained in urine is substituted by hydrogen ions of the macromolecular electrolyte to release hydrogen ions resulting in pH change that is detected with pH indicator. However, it is currently difficult to yield the urine specific gravity from cation concentration due to the changed eating habits of Japanese people. Therefore, a proposal of measuring method using test paper was made for knowing the urine specific gravity from urine concentration (the publication of patent applications 1993-180846). For example, coloring test tool is constituted by attaching a base material such as filter paper, to which urease, pH indicator, and buffer solution have been applied, to a supporter such as polystylene. Urea contained in urine is decomposed by urease on the coloring test tool. PH changed by ammonia generated by the decomposition is detected with the pH indicator to measure urine concentration.
On the contrary, urine specific gravity is changed according to two components of sodium chloride (10-15 g/day) and urea (15-30 g/day) as principal solute components (Rinsyou Byouri. November extra issue: 98-108. 1995). Therefore, when cations or urea concentration is individually measured to know urine specific gravity on the basis of correlation, the gravity yielded probably has an error.
Prior art related to the measurement of urinary glucose value has the following defects.
First, the prior art does not allow to make simple and accurate measurement of urine specific gravity. The reason is that the estimation of urine specific gravity by measuring cations or urea concentration individually using test paper has the error, because urine specific gravity is primarily determined by sodium chloride concentration and urea concentration both contained in urine.
Second, the prior art does not allow to estimate simply urinary glucose value contained in total urine excreted for 24 hours on the basis of the urinary glucose value of a partial urine. The reason is that the urinary glucose value of a partial urine differs from the urinary glucose value contained in total urine excreted for 24 hours,because the former urinary glucose value is affected by urine volume.